<template>
    <div>
        <router-link tag="div" to="/" class="header-abs" v-show="showAbs">
            <div class="iconfont header-abs-back">&#xe624;</div>
        </router-link>

        <div class="header-fixed" v-show="!showAbs" :style="opacityStyle">
            大连圣亚海洋世界(AAAA景区)
            <router-link to="/">
                <div class="iconfont header-fixed-back">&#xe624;</div>
            </router-link>
        </div>
    </div>
</template>
<script>
export default {
    name:'DetailHeader', 
    data () {
        return {
            showAbs:true,
            opacityStyle: {
                opacity:0
            }
        }
    },
    methods:{
        handleScroll () {
            const top = document.documentElement.scrollTop
            if(top>60){
                let opacity = top / 140
                opacity = opacity > 1 ? 1 : opacity //渐隐渐现
                this.opacityStyle = { opacity }
                this.showAbs = false
            }else{
                this.showAbs = true
            }
        }
    },
    activated () { //页面展示被执行,这里面有个问题是全局绑定,所以要解绑，使用keep-alive 就不起作用  
        window.addEventListener('scroll',this.handleScroll)
    },
    deactivated () { //页面隐藏之后被执行
        window.removeEventListener('scroll',this.handleScroll)
    }
}
</script>
<style lang="stylus" scoped>
@import '~styles/varibles.styl'
.header-abs
    position:absolute
    left:.2rem
    top:.2rem
    width:.8rem
    height: .8rem
    line-height: .8rem
    border-radius: .4rem
    text-align: center 
    background:rgba(0,0,0, .8)
    .header-abs-back
        color:#fff
        font-size: .4rem
.header-fixed
    z-index: 2
    position:fixed   //为了显示iconfont
    top:0
    left:0
    right:0 
    height :$headerHeight
    line-height :$headerHeight
    text-align :center
    color:#fff
    background:$bgColor
    font-size:.3rem
    .header-fixed-back
        position:absolute //为了显示iconfont
        top:0             //为了显示iconfont
        left:0            //为了显示iconfont
        width:.64rem
        text-align:center
        font-size: .4rem
        color:#fff        
</style>
